We shall examine a family of heavy atom containing test materials to determine the resolution of our instrument and the dosage tolerance of various samples. We shall label homopolynucleotides, simple satellite nucleic acid molecules and natural nucleic acid molecules with our C specific reagent. Then, after osmium binding, we shall observe them in our high resolution STEM. On the basis of electron micrographs, we shall attempt to infer nucleotide sequence. We shall examine TMV, RNA polymerase and actin after labeling with various amino acid specific heavy atom labels. This will test protein labeling procedures in structure analysis. BIBLIOGRAPHIC REFERENCE: Trimethyl-lead Acetate as a DNA Backbone Stain for Electron Microscopy. A. Kosiara, K. Douglass and M. Beer. Proceedings of 33rd EMSA Meeting, p. 264, Las Vegas 1975.